Vaccination opportunity in children up to 6 months old born in 2017 and 2018 in the city of Londrina-PR, Brazil: a population-based survey.

Objective: To evaluate opportunity for vaccination in children born alive in Londrina, up to 6 months old and the relationship between socioeconomic stratum and vaccination regularity.

Method: Population survey study based on a retrospective cohort of children born in 2017 and 2018 that identified vaccines not administered in a given session. Vaccination regularity was compared between socioeconomic strata using Pearson's chi-square test.

Results: Out of 456 vaccination cards, the proportion of vaccination opportunities not recovered for doses to be administered at birth and at two, four and six months was 5.0% (95%CI 3.1;7.5), 4. 5% (95%CI 2.8;6.9), 7.2% (95%CI 5.0;10.2) and 2.1% (95%CI 1.0;4.0), respectively. There was no statistical difference in vaccination regularity between the strata.

Conclusion: Missed opportunities for vaccination were found at all ages. Socioeconomic stratum did not influence vaccination regularity.